三螺杆挤出机啮合块混合特性的数值模拟

Numerical Simulation on Mixing Characteristics of Kneading Blocks in Tri-screw Extruders

利用流场分析软件Polyflow对啮合块在不同参数下的等温稳态流场进行数值模拟。同时引入加权平均剪切应力,加权平均剪切、拉伸速率和回流系数等不同的评价指标以表征倒三角形三螺杆挤出机的混合性能。深入分析不同因素对啮合块混合特性的影响。结果表明:啮合块具有优异的分布和分散混合性能。啮合盘厚度增加导致流场中拉伸作用增强。增大错列角会使正向啮合块的剪切降低,拉伸增强,反向啮合块的趋势则与之相反;为啮合块的设计提供了依据。

Three-dimensional isothermal flows of kneading blocks were simulated using an analysis package Polyflow. At the same time,weighted average shear stress, weighted average shear rate and stretching rate, backflow ratio and so on were brought in to characterize and analyse the mixing performance of triple-screw extruder. The mixing performance of kneading blocks with different parameters was deeply analysed. It was found that the kneading blocks had excellent dispersion and distribution mixing performance. Extensional actions of the flow field increased along with the kneading blocks thickness. With the increase of staggered angle, the shear action of forward kneading blocks decreased and the extensional action increased, while the actions of reversed kneading blocks were just the opposite. All of these laid a foundation for the design of the kneading blocks.